So it's been 3 months and the original thumbnail for this beatmap is still show in game. Will it ever change to the updated thumbnail? And is there anyway to fix it at this point? Yes, I've reloaded the map in osu and downloaded it from the site several times, but it seems to be the same for anyone who downloads it. link to map: https://osu.ppy.sh/s/606698

The old thumbnail is the same for anyone who had downloaded the map before you update its thumbnail. That's because osu! has saved this beatmap with the original thumbnail and it won't update to the new one unless you manually delete it. To do so, go to your osu! folder, open the Data folder (it's hidden so make sure to enable the option to view hidden files), and then the bt folder. There, find your beatmap's old thumbnail and delete it. The game should update the map instantly.

Nikosbks wrote:

The old thumbnail is the same for anyone who had downloaded the map before you update its thumbnail. That's because osu! has saved this beatmap with the original thumbnail and it won't update to the new one unless you manually delete it. To do so, go to your osu! folder, open the Data folder (it's hidden so make sure to enable the option to view hidden files), and then the bt folder. There, find your beatmap's old thumbnail and delete it. The game should update the map instantly.